Cars that sit in the hot sun will have the interior heat up dramatically. Plastic parts in the interior have whats called plasticisers added to keep them from cracking. In a hot interior, the plastic releases a vapor known as plasticiser vapor. This vapor creates a film on the inside of glass windows. To keep this to a minimum, periodically wipe down all interior dash, doors, etc. with a mild soap and water solution. Dip your micro-fiber towel, or other clean rag, in solution....wring out and wipe down. See my article on creating a simple and cheap glass cleaner to learn the best way to get rid of this film on inside of front windshield. To get more Auto Detailing tips go to my Blog at Nu-Sheen-Blog.com . Also check out Meltdown Bug Remover.